I play in a 5 person bluegrass band. The mandolin player is a gifted musician, and a wonderful harmony singing partner. He also stutters very noticeably when speaking--but never when singing.

As for the alzheimer patients, I have played for many of
them in nursing homes. Many of them are almost
catatonic. However, some of them still respond when
they hear music, either by smiling, clapping or foot tapping.